#include <bits/stdc++.h>
using namespace std;
using uint=unsigned int;
using ll=long long;
using ull=unsigned long long;
using i128=__int128;
const int N=1e6+5;

void solve(){
    
    return;
}

int main(){
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr); std::cout.tie(nullptr);
    ll a,b,n;
    cin>>a>>b>>n;
    ll w=5*a+2*b;
    ll ws=n/w;
    ll c=n%w;
    ll d=7*ws;
    if(c<=5*a){
        if(c%a==0)d+=c/a;
        else d+=c/a+1;
    }
    else{
        if((c-5*a)%b==0)d+=(c-5*a)/b+5;
        else d+=(c-5*a)/b+6;
    }
    cout<<d<<endl;


    return 0;
}